Down lighting apparatus



April, i6, 1946. T. w. RoLPH 2,398,507

DOWN LIGHTING APPARATUS Filed Feb. 5, 1944 2 Sheets-Sheet l llllllllHl I llllllIlll IIHIIIHIII umnmuluummnw lllllllllllllm"l TOR LPI-l ATTORNEY April 16, 1946'. 1,-, w. RoLPH 2,398,507

DOWN LIGHTING APPARATUS Filed Feb. 5, 1944 2 Sheets-Sheet 2 INVENTOR THOMAS W. PULP# Patented Apr. 16, 1946 UNITEDi STATES PATENT OFFICE DOWN LIGHTING APPARATUS kThomas W. Rolph, Newark, Ohio, asslgnor to Holophane Company, Inc., New York, N. Y., a

corporation of Delaware Application February 5, 1944, serial No. v521,167

(ci. 24o-9) 8 Claims.

objects in the room, and hence the brightness contrasts are very high. Owing to the losses in the reflectors used to get the light out of the luminaries refe'rred to and the interception of light by other lamps in the same unit, the utilization factor is comparatively low.

The present invention contemplates down lighting apparatus wherein the entire overhead surface area is in the form of light transmitting plates and all these plates are rendered luminous so that the entire ceiling is lighted up with comparatively small differences in brightness at the ordinary angles of observation.

A further object of the present invention is to eliminate much of the expense of lamp boxes, wireways and false ceiling supports customarily employed, and to reduce the mechanical features of the installation to their simplest terms, for example, lamps, lamp sockets or holders supported from the original ceiling or from the lens supports, lens plates and filler plates, channels or T-bars suspended from the original ceiling and supporting the plates, lamp auxiliaries supported in any convenient way between the two ceilings and serving lamps in pairs or fours as desired, and wiring in BX or wire mold or similar simple construction. No box or enclosure of sheet metal or other material is required. All, parts between the two ceilings would ordinarily be painted white in so far as practical.

The accompanying drawings show, for purposes of illustrating the present invention, several embodiments in which the invention may take form, it being understood that the drawings are illustrative of the invention rather than limiting the same.

In these drawings:

Figure 1 is a cross section and semi-perspective view showing the general arrangement ofthe down lighting apparatus;

Figures 2A, 2B and 2C are diagrammatic inverted plan views of a ceiling equipped with the down lighting apparatus;

Figure 3 isa cross sectional view showing an optical action of one form of construction and omitting structural features;

Figure 4 is a detailed sectional view through typical prisms of a iiller plate; and

Figures 5 to 9. inclusive, are views similar to Figure 3 showing modified forms of construction.

In Figure 1 the superstructure I0 may be the original ceiling, or the bottom of the floor slab. At suitably spaced intervals the superstructure, or ceiling. carries longitudinally extending supports Il. Rectilinear lamps I 2 are suitably mounted below the ceiling I0 and are preferably placed halfway between certain of the supports II.

'I'he supports I I, which are closest to the lamps I2, support prismatic lens plates I3, I3 of alight concentrating type in rows corresponding with the length of the lamp or lamps employed. The spaces between the rows oi.' lens plates I3, I3 are occupied by nller plates I4, I4. The lens plates and filler plates may be any size convenient for handling.

The dominant feature resides in the use of lens plates and intermediate filler plates. The lamps, lenses and plates may be placed in parallel rows extending lengthwise of the ceiling area as in Figure 2A, or the ceiling plan arrangement may be varied to suit, as, for example, shown in Figures 2B and 2C. The lamps and rows of lenses and plates may extend diagonally of the ceiling space, if desired.

. may be mere diffusing plates, if desired. rIjhe ceiling I0 has a diffuse reflecting surface, for example, white paint. The lens plates are preferably made of the maximum width by which light can be concentrated to the desired extent by dioptric prisms. For regularity of appearance and flexibility of mounting the widths of plates I3 and I4 are preferably the same. The plates I4 accept direct rays, such as indicated at I6, I6, Figure 4, from the lamps I2, I2 and reflect these rays downwardly as indicated at II, I1, and, if desired, these rays may becaused to slightly diverge by providing the bottom of the plates with diil'using u'tes I8. i

In the arrangement shown in Figures 3 and 4 direct light through a very wide angle each side of the nadir is accepted by the plates and transmitted into the desired directions. The upwardly emitted light is intercepted by the ceiling and diffusely reflected downwardly where it adds to the general downwardly directed illumination. In

this arrangement the plates are shown flat and lamp obstruct the light from another, as is common in fluorescent lighting equipment employing two or more comparatively closely placed lamps. Furthermore it is possible to make the equipment very shallow, for example, the lens plates one foot wide need be only 4 inches or 5 inches below the reecting surface of the ceiling.

The prisms I5 preferably have an apex angle of approximately 60 and the prism surfaces may be plane or curved. These prisms will receive light from the lamps between angles of 60 and 90 from the nadir and reiiect such light downwardly with high eiiiciency.

In the arrangement shown in Figure 5 the vprismatic lens plate I3 is the same as before, but two filler plates 20, 20 are used andeach slopes upwardly from the adjacent edge of the light concentrating plates I3 so that all the light emitted below the horizontal is intercepted by plates I3- and 20 or 20. Plate 20 is shown as having refracting prisms 2I which lower the light as indicated, while the plate 20' is shown with reecting prisms for the same purpose. The ceiling I0 diffusely reflects the light as before.

In the arrangements shown in Figures 6 to 8, inclusive, the light concentrating plates 22 are dished so as to intercept more of the light emitted by the lamps below the horizontal than the flat plates I3. The filler plate 23 of Figure 6 receives no direct light, but does receive light diiiusely reflected down by the ceiling I Il, and this plate may therefore be a simple diffusing plate. The plates 24 and 25 of Figures 7 and 8 receive light reected toward them by the specular reflectors 26 and 21, respectively, and the plates 24 and 25 are therefore preferably reflecting plates of the type indicated in Figure 4.

In the arrangement shown in Figure 9 the lens plates 26 under the lamps are of the light spreading type and they may be used with filler plates 2l of any of the forms above discussed. Such lens plates will provide a more extensive distribution of light.

It will be noted that the down lighting apparatus shown herein is one wherein the lighting equipment typically occupies a large portion of the ceiling area and may be rendered luminous when in operation. It therefore has much less brightness contrast than ceiling constructions wherein part of the ceiling is illuminated only by reiiected light. It also has less maximum brightness than ceiling constructions using the same size and amount of lighting equipment, but having reflectors which send the light downwardly and therefore build up the amount of light which must be transmitted through the narrowed region.

The equipment is one which has a high elciency of light utilization and it is readily possible to obtain varied intensities of illumination by varying the number of rows of filler plates used foreach row of lens plates. If, for example, the rows of lens plates and filler plates be alternated and a certain average horizontal illumination be obtained, then it is possible to obtain two-thirds of this illumination by using two rows of filler plates between each row of lens plates; or it is possible to obtain one-half the original illumination by using three rows of flllerplates between each row of lens plates. In locations where extremely high illumination intensities are desired. the entire area may be covered with lens plates with one or more lamps over each plate.

In practicing the present invention it is possible to use plates which are fiat or dished, horizontal, or sloping and provided with refracting prisms near the lamps and with reiecting or refracting prisms more remote from the lamps, or in the latter location, diifusing plates may be used. The arrangement of light controlling prisms is designed for optical control of the light rays, while the size of the plates on which the prisms (or diffusing surfaces where used) are disposed is determined by convenience in manufacturing methods and installations. The reflecting surface above the lamps may be specular, semi-specular or diil'use and of suitable contour.

Since it is obvious that the invention may be embodied in other formsand constructions within the scope of the claims, I wish it to be understood that the particular forms shown are but a few of these forms, and various modifications and changes being possible, I do not otherwise prisms when embodied in a plate, the plates acting to symmetrically alter the spread of light from the corresponding superposed lamps and direct the transmitted rays into beams with controlled spread toward regions of a working area underneath and to each side of said corresponding lamps, the lamps being laterally spaced from one another to leave spaces between adjacent edges of the prismatic plates of substantial width, and light redirecting iiller plates occupying the said spaces and being disposed between the refracting plates, the filler plates receiving light originating in the adjacent lamps and emitted at angles above the edgesvof the refracting plates and reflected downwardly from said reecting surface and transmitting suchv light in generally downward directions whereby substantially all the light emitted by the lamps is received by the plates either as direct light or as once reected light, and all the plates appear luminous, the iiller plates acting to build up the light ux received 'in said working area, beneath the filler plates.

2. Apparatus as claimed in claim 1, wherein all the plates are flat and at a common level with the refracting plates so that the ller plates receive direct light.

3. Apparatus as claimed in claim l, wherein all the plates are flat and at acommon level With the refracting plates so that the filler plates receive direct light and the filler plates are provided with light directing ribs parallel with the sources and disposed to accept direct light and bend it downwardly.

4. -Apparatus'as claimed in claim 1, wherein the ller plates are flat and at a common level with the refracting plates so that the filler plates receive direct light and are provided on their upper surfaces with light reecting ribs parallel to the sources which reilect light generally downwardly.

5. Apparatus as claimed in claim 1, wherein the ller plates are ilat and at a common level with the refracting pl-ates so that the filler plates receive direct light and are provided on their upper surfaces with light reilecting ribs parallel to the adjacent sources which reflect 'light generally downwardly, and diffusing flutes on the lower surface which scatter light laterally.

6. Apparatus as claimed in claim 1, wherein two ller plates are employed between adjacent refracting plates and they extend upwardly from the edges of therefracting plates to substantially the level of the lamps so as to receive light emitted between the horizontal and the refracting plates and have light depressing prisms.

7. Apparatus as claimed in claim 1, wherein the light refracting plates are dished to accept substantially all direct light below the horizontal and the ller plates are substantially at the level of the sources.

8. Apparatus as claimed in claim 1, wherein the reflecting surface includes specular reflectors disposed to reflect light on to the filler plates, and wherein the refracting plates are dished to accept substantially all direct lightbelow the horizontal and the illler plates are substantially at the level of the sources and the filler plates are provided with ribs parallel with the sources which reect light downwardly.

THOMAS W. ROLPH. 

